The dumb questions thread

[Wiploc]

Sounds like you're talking about point X's point of view.

Suppose we're you, in your point of view. We think we're stopped, right, because everything is stopped relative to itself. And the light from X is blue-shifted, but still moving at c, relative to us.

But X itself is approaching at 2c, ahead of it's light. Its light trails behind it like the wake of a fast boat. And you can't detect the boat by feeling its wake, because the boat gets to you ahead of the wake.

At last, I understand why people think you can't see at superluminal speeds.

Sure, but it's a reasoning error. The assumption that relative to you the light from X is approaching you at c is based on the premise that relativity is true. The assumption that you're headed towards point X at 2c is based on the premise that relativity is false. You need to use consistent premises. That means if you want to figure out what will happen if you're approaching X at 2c, you need to discard Special Relativity and switch to Lorentz Ether Theory. In LET, superluminal observers aren't going to observe light always traveling at c.

I think that works if you were moving slowly relative to the mime early on. I'm not sure it works if the mime has always been approaching at 2c.

The mime isn't approaching you at all. You're approaching the mime. The principle that those are the same thing goes away in LET.

Thanks for the feedback. Does relativity really forbid tachyons? I thought it forbade matter traveling at c, but allowed it to go either faster or slower.

 

[Loren Pechtel]

You can still look forward even if you're going FTL. (Now, whether your optics can work is another matter...) You get the same starbow effect of relativistic velocity except even more so.

Now, if something appears in your path that's another matter, you're not going to see it.

I'm not sure what you're saying, so I'll create a hypothetical to see if it illuminates things for us.

Suppose you are 100 light years from point X, and headed towards point X at 2c, and at this moment, a mime in an actual glass box teleports to point X.

Question: Will you see the mime in time to evade?

First answer: You will see the mime when you are 33 light years from X. You'll move 66 light years while the light from the mime moves 33.

Objection to first answer: I don't even know whose point of view I'm talking about. Let's try to establish a point of view, and see what that looks like.

Suppose we're you, in your point of view. We think we're stopped, right, because everything is stopped relative to itself. And the light from X is blue-shifted, but still moving at c, relative to us.

But X itself is approaching at 2c, ahead of it's light. Its light trails behind it like the wake of a fast boat. And you can't detect the boat by feeling its wake, because the boat gets to you ahead of the wake.

At last, I understand why people think you can't see at superluminal speeds.

But, yes, the mime has to teleport in front of you for this to work? Otherwise there would be a beam of light ahead of her that you could see?

I think that works if you were moving slowly relative to the mime early on. I'm not sure it works if the mime has always been approaching at 2c.

Good point, you still see it, just not with a lot of warning.

 

[skepticalbip]

Sounds like you're talking about point X's point of view.


Sure, but it's a reasoning error. The assumption that relative to you the light from X is approaching you at c is based on the premise that relativity is true. The assumption that you're headed towards point X at 2c is based on the premise that relativity is false. You need to use consistent premises. That means if you want to figure out what will happen if you're approaching X at 2c, you need to discard Special Relativity and switch to Lorentz Ether Theory. In LET, superluminal observers aren't going to observe light always traveling at c.


The mime isn't approaching you at all. You're approaching the mime. The principle that those are the same thing goes away in LET.

Thanks for the feedback. Does relativity really forbid tachyons? I thought it forbade matter traveling at c, but allowed it to go either faster or slower.

You are right that relativity doesn't forbid greater than c but greater than c would have some damn weird "realities" (at least according to the math of relativity). For instance time would be imaginary whatever the hell that means. I suppose mathematically that would mean that time in a FTL reality would be orthogonal to time below c if that means anything. Also applying force would slow the tachyon and an infinite amount of force would be required to slow it to c sorta like an infinite force is required to accelerate matter up to c and so the reason it is impossible to accelerate to c from either direction.

Personally, I don't think there is any such thing as tachyons but, who knows, reality has already shown us some damn weird things - for instance, black holes.

 

[Loren Pechtel]

No. It's not going to be blue-shifted to gamma. At 1.5c you're hitting the waves at 2.5x the rate you would if you're standing still. Visible light isn't going to be shifted beyond the near ultraviolet by that kind of speed. You're going to need something over 100,000c to shift visible light into the gamma part of the spectrum.

You're describing the ship/light interaction from the point of view of the star. What you're actually going to experience will be from the point of view of the ship, and that means the whole universe is foreshortened and the waves along with it. At c the wavelength is foreshortened to zero and the blue shift is infinite. God knows how foreshortened they are at 1.5c.

At c photons would be red shifted to infinity. The only reason you would get an infinite blue shift is because time would stop at c--but that doesn't apply when you're superluminal.

 

[steve_bank]

I do not know enough of the math to make serious arguments, but I have always had a nagging feeling there are holes in it in terms of demonstration. It is untestable in some respects.

It took three or four centuries to go from Newton to Einstein, Maxwell, and QM. Newton was preceded by a lot of work on what became his mechanics and calculus.

It could take a thousand years to advance beyond current science. And we are limited by instrumentation.

In a simulation based on the math as a ship accelerates at 1g what happens as the ship approaches C in the ship's frame?

People standing on the floor orthogonal to the engine thrust will see 1g. The mass of the ship does not change in its frame.

Magic propulsion assumed. The propulsion system adjusts thrust at all times to maintain 1g. What do the occupants of the ship experience?

I'd be surprised if the simulations have not been done.

In the 50s I renumber a prime time show on relativity. AE had rock star status. An animation showed a spaceship getting smaller.

 

[skepticalbip]

In a simulation based on the math as a ship accelerates at 1g what happens as the ship approaches C in the ship's frame?

Inside the ship (not looking outside) the observer would see and experience everything as anyone in any vehicle accelerating at 1g anywhere else, In fact, they would experience no difference than if the ship were were sitting on the launch pad here on Earth.

People standing on the floor orthogonal to the engine thrust will see 1g. The mass of the ship does not change in its frame.

I don't follow that.

Magic propulsion assumed. The propulsion system adjusts thrust at all times to maintain 1g. What do the occupants of the ship experience?

For the ship to continuously accelerate at 1g as measured in the ship, the thrust must remain constant (ignoring that the mass of burnt fuel has been ejected from the thruster). As measured in the ship there is no difference in 1g acceleration just starting the trip and after having accelerated at 1g for ten years.

I'd be surprised if the simulations have not been done.

If you mean what it looks like for those in the ship looking out then yes it has. But remember, if the ship has no windows then those inside can not tell the difference between sitting on the launch pad at Cape Canaveral and continually accelerating through space at 1g. That is because all reference frames are equally valid.

 

[steve_bank]

Inside the ship (not looking outside) the observer would see and experience everything as anyone in any vehicle accelerating at 1g anywhere else, In fact, they would experience no difference than if the ship were were sitting on the launch pad here on Earth.

I don't follow that.

Magic propulsion assumed. The propulsion system adjusts thrust at all times to maintain 1g. What do the occupants of the ship experience?

For the ship to continuously accelerate at 1g as measured in the ship, the thrust must remain constant (ignoring that the mass of burnt fuel has been ejected from the thruster). As measured in the ship there is no difference in 1g acceleration just starting the trip and after having accelerated at 1g for ten years.

I'd be surprised if the simulations have not been done.

If you mean what it looks like for those in the ship looking out then yes it has. But remember, if the ship has no windows then those inside can not tell the difference between sitting on the launch pad at Cape Canaveral and continually accelerating through space at 1g. That is because all reference frames are equally valid.

Thanks. I keep getting hung up on C as an unsurpassable limit for accelerating mass. Everything looks normal in the ship, a kg is still a kg. As the ship approaches C what happens?

From the equation energyrequired goes to infinity asymptotically.

Is this relative to say the Earth's surface as another frame? If so then I come back to whether C is a limit or not. If everything look Newtonian in the ship, what presents the C limit?

 

[skepticalbip]

Is this relative to say the Earth's surface as another frame? If so then I come back to whether C is a limit or not. If everything look Newtonian in the ship, what presents the C limit?

.. The dimensions of velocity is meters per second and such a measurement requires a 'stationary' reference point.
.. The dimensions of acceleration is meters per second squared and such a measurement does not require an external reference point... an accelerometer measures force.

.. The second as measured within a ship moving at relativistic velocity with respect to a 'stationary' reference point will be significantly longer than an observer at that 'stationary' reference will measure it so will see the ship's clock running slower and slower as the ship continues to accelerate.
.. A meter as measured within a ship moving at relativistic velocity with respect to a 'stationary' reference point will be significantly shorter than an observer at that 'stationary' reference will measure it so will see the ship getting shorter and shorter as it continues to accelerate.

This means that when those in the ship traveling at relativistic velocity with respect to some 'stationary' reference measure their acceleration at 1g (9.8 of what they measure as a meter divided by what they measure as a second squared), those at the 'stationary' reference will measure the ship's acceleration as much less. Throughout the trip those in the ship will measure their acceleration at a constant 1g but those at the 'stationary' reference will measure the ship's acceleration rate as constantly decreasing asymptotically toward zero as the ship approaches a relative velocity of 3 x 10^8 m/s.

If you have difficulty breaking away from a Newtonian view of the universe and accepting a relativistic view then you probably need to do the math until you get a feel for relativity.

ETA:
The neat effect of this is that someone, in only a few years by their biological clock, can visit a planet in a star system a few thousand light years away from Earth if there is a magic propulsion system that can accelerate them at 1g the entire trip, However those they left on Earth will see the trip as taking several thousand years.

 

[Bomb#20]

Thanks for the feedback. Does relativity really forbid tachyons? I thought it forbade matter traveling at c, but allowed it to go either faster or slower.

Well, I'm not up on tachyon theory, so take this with a grain of salt, but here are my 2 cents...

By your suppositions, you're headed toward X at 2c. That means you're made of tachyons. What will you see? That depends on what we assume about tachyon physics. Is it even possible to build a clock and a measuring stick and a photon detector out of tachyons? Assuming so, is it true that you think you're stopped? Tachyons allegedly always move faster than c. Why wouldn't a tachyon physicist know that? Geometry and topology would be seriously different for tachyon organisms -- you can't even reverse direction by slowing down to zero and then speeding up -- so it's not clear that relativity's claim that all reference frames are created equal applies to superluminal ones.

Which brings us to your central claim: "X itself is approaching at 2c, ahead of it's light." I don't think that follows. What's at X emitting light is, per your suppositions, an actual glass box. It can't be approaching at 2c. It's made of glass, not tachyons. Relativity according to some interpretations allows for tachyons, but is that supposed to mean that which particles are tachyons and which particles are fermions is itself observer-relative too? That I haven't heard, and it seems improbable. Is there really no experiment a tachyon physicist could do to tell he was made of tachyons? As tachyons lose energy they speed up. That sounds noticeable.

 

[steve_bank]

You are on a spinning mass the size of the Erath with no atmosphere. A ball at rest to the surface is dropped from some altitude. Does it fall straight down?

Can't remember the name, there was an ancient female mathematician who allegedly tried the experiment on a boat. Drop the object from the mast of a moving boat and see where it lands.

 

[skepticalbip]

You are on a spinning mass the size of the Erath with no atmosphere. A ball at rest to the surface is dropped from some altitude. Does it fall straight down?

Can't remember the name, there was an ancient female mathematician who allegedly tried the experiment on a boat. Drop the object from the mast of a moving boat and see where it lands.

^^^
If anyone is uncertain then this (quite old) video would be well worth their viewing even though it is almost 30 minutes. It is part of an old introductory physics presentation on reference frames.

[video]https://archive.org/details/frames_of_reference[/video]

 

[bilby]

You are on a spinning mass the size of the Erath with no atmosphere. A ball at rest to the surface is dropped from some altitude. Does it fall straight down?

I don't know - I am too busy dying of anoxia, and suffering the effects of exposure to vacuum and cosmic radiation to care.

 

[bigfield]

You are on a spinning mass the size of the Erath with no atmosphere. A ball at rest to the surface is dropped from some altitude. Does it fall straight down?

No, because of  Coriolis force.

The ball's actual trajectory depends on the following:
1. Its mass
2. Its starting altitude
3. Its starting latitude

If its mass is too low or its altitude is too high, the ball might not fall at all.

 

[Jimmy Higgins]

You are on a spinning mass the size of the Erath with no atmosphere. A ball at rest to the surface is dropped from some altitude. Does it fall straight down?

What force would act on it laterally to make it not fall "straight down"? It won't land at the point directly underneath at release due to its rotation, but it will fall "straight down".

 

[Wiploc]

You are on a spinning mass the size of the Erath with no atmosphere. A ball at rest to the surface is dropped from some altitude. Does it fall straight down?

Pretty much, for small values of "some altitude."

When you stand up, your head is going around the earth faster than your feet, but this is negligible, not noticeable. A ball dropped from beside your head would land beside your feet, and it would take some pretty sophisticated equipment to determine that it didn't fall straight down.

But, now suppose you are standing at the equator, traveling around the world at about 1000 miles an hour. You're about 4000 miles from the center of the earth. And suppose that a ball is dropped (or thrown, if necessary--it might be in orbit or something) from a vessel twice as high, 4000 miles above you. That means the ball would be going, let's see, <consults Big Book of Red Rubber Ball Trajectories>, 2000 miles an hour, twice as fast as you, which means it wouldn't fall anything like straight down.

Google finds me a claim that orbital velocity is 25,000 miles an hour, so the ball probably does fall down rather than float away.

So, the answer: the ball does fall, and at first it seems to be falling straight down. But, the closer it gets to you, the more it seems to veer away east. It continues to "accelerate" east until it catches atmosphere and is slowed down relative to the surface.

 

[Wiploc]

You are on a spinning mass the size of the Erath with no atmosphere. A ball at rest to the surface is dropped from some altitude. Does it fall straight down?

What force would act on it laterally to make it not fall "straight down"? It won't land at the point directly underneath at release due to its rotation, but it will fall "straight down".

Rationalized that way, every ball falls straight down.

 

[Jimmy Higgins]

You are on a spinning mass the size of the Erath with no atmosphere. A ball at rest to the surface is dropped from some altitude. Does it fall straight down?

What force would act on it laterally to make it not fall "straight down"? It won't land at the point directly underneath at release due to its rotation, but it will fall "straight down".

Rationalized that way, every ball falls straight down.

Glad you agree. [emoji16]

Also, my understanding was the ball was at rest, to me that means horizontally as well, so no radial velocity.

 

[Jokodo]

As you approach c relative to the star, the light from the star (even the really long radio waves) is blue-shifted to gamma. It's going to pass through a mile of depleted uranium shielding practically unchanged - how would you detect such hugely energetic, super high frequency gammas?

But there's a bigger problem - why are you surprised that you are pointing at the star? Surely you knew it was there to begin with. But having accelerated "beyond" c, you have given yourself less than no time to steer - at 1.5c, you hit the farthest away stuff on your trajectory first.

Presumably.

Fucked if I know what happens at tachyonic velocities. I'm just guessing

No. It's not going to be blue-shifted to gamma. At 1.5c you're hitting the waves at 2.5x the rate you would if you're standing still. Visible light isn't going to be shifted beyond the near ultraviolet by that kind of speed. You're going to need something over 100,000c to shift visible light into the gamma part of the spectrum.

Is that taking time dilation into account?

 

[Jokodo]

You are on a spinning mass the size of the Erath with no atmosphere. A ball at rest to the surface is dropped from some altitude. Does it fall straight down?

Can't remember the name, there was an ancient female mathematician who allegedly tried the experiment on a boat. Drop the object from the mast of a moving boat and see where it lands.

That depends on altitude and latitude - to take an extreme example, if the ball starts out "at rest to the surface" at the equator at a geostationary distance (or even higher), it won't fall down at all.

Anywhere not above the equator it will appear to be diverted towards the equator - it's initial momentum is along a great circle route, not along the equator - and ahead in the direction of rotation - it's moving faster than the surface beneath it. Or maybe behind because the points closer to the equator are moving faster than where it started? I'd have to read it up and/or do the math, but as an off-hand guess, this too might depend on initial altitude.

For low altitudes: straight enough for the motions of the sea to be the dominant factor by far with this setup, even on a calm day.

 

[Jokodo]

In other words, any object in motion above a planet's surface, such as your ball, is an object in orbit around the planet's center of mass (only slightly simplifying by ingoring unequal mass distribution), unless it is moving above escape velocity. Whether and where it hits the ground is where it's orbital trajectory intersects the surface.