The dumb questions thread

[bilby]

If you were traveling in the dark in your spaceship just shy the speed of light and cut your headlights on, you should be able to see, but my question is, if you were traveling at the speed of light and did the same, does light illuminate ahead?

If you cannot overlook the apparent impossibility of traveling near or at the speed of light, then let me ask this instead: if our planet within our solar system is orbiting the center of our galaxy at speed S, then is the speed of the particular light being shined from my super duper lantern essentially traveling at an increased speed of C minus S? I mean, if light can only go C and the first light wave automatically starts out traveling S, then it can't exceed the additional difference without it exceeding its maximum.

Light travels at c in a vacuum relative to an observer, regardless of how the observer is moving. What varies is how time passes for observers in different reference frames.

If I am drifting in space, watching you go past in your spaceship at 0.99c, then you turn on your headlights, from my perspective, the light comes from your lights at c, so it is only moving 0.01c faster than you are. But from your perspective on board the ship, it moves ahead of you at c, not 0.01c. The reason for our disagreement about how much faster than your ship the light propagates is that you and I don't agree on how long a second is. Your clock appears to me to be running very slowly, so I am unsurprised that you think the light is going away from you faster than I can see it is. Moving clocks run slowly, when measured in an inertial frame. http://math.ucr.edu/home/baez/physics/Relativity/SR/movingClocks.html

You can't travel at c, unless you have zero rest-mass. So the question regarding travel at exactly c is unanswerable; At that speed, your clock (as measured from my inertial frame) is stopped, and any speed calculation involves a division by zero. To a photon, everything happens at the same time, and the concept of speed (distance divided by time) is meaningless.

 

[Loren Pechtel]

If you were traveling in the dark in your spaceship just shy the speed of light and cut your headlights on, you should be able to see, but my question is, if you were traveling at the speed of light and did the same, does light illuminate ahead?

<Error: No time to turn on the lights--time stops at c>
<Error: Universe crushed out of existence--infinite mass at c>
<Error: Insufficient fuel--infinite fuel is needed>

If you cannot overlook the apparent impossibility of traveling near or at the speed of light, then let me ask this instead: if our planet within our solar system is orbiting the center of our galaxy at speed S, then is the speed of the particular light being shined from my super duper lantern essentially traveling at an increased speed of C minus S? I mean, if light can only go C and the first light wave automatically starts out traveling S, then it can't exceed the additional difference without it exceeding its maximum.

You will measure it as going at C. That's the heart of special relativity.

Einstein noted that all measurements of lightspeed agreed no matter the speed or direction of the observer. This was his starting point--assume light will move at c no matter what. He then figured out what was needed mathematically so observers would agree on this--and ended up with something mathematically consistent. He published it--we know it as special relativity. Since then we have found various ways to actually measure the effects and they agree with his work. We also have the GPS system which provides a practical example--ordinary civilian GPS operates at a precision well in excess of the Newton/Einstein differences even given the tiny fraction of lightspeed at which the satellites orbit. (And the fact that the satellites are way up there instead of on the ground also matters.) Note, furthermore, that sufficiently sophisticated receivers are capable of 3+ more digits of precision--for those receivers the Newtonian answer is more than a thousand times as wrong as the inherent error of the equipment. (And the reason you don't see those receivers on the market is that they can't be made small (fancy antennas are required, not the simple omnidirectional antenna in your navigation device) and they can't be made portable--you have to set them up at a location and leave them running in order to get that kind of precision. They're used by surveyors and geologists (tracking ground movement), not by travelers.)

 

[another1]

Can I befriend a feral cat without using food? Just wondering if there are any other ways.

 

[Wiploc]

If you were traveling in the dark in your spaceship just shy the speed of light

All motion is relative. You are always stopped relative to yourself, and you are always traveling near the speed of light relative to cosmic rays.

If you want to see what happens when you turn a flashlight on near the speed of light, turn on a flashlight.

and cut your headlights on, you should be able to see, but my question is, if you were traveling at the speed of light and did the same, does light illuminate ahead?

At the speed of light? That involves something like dividing by zero. My physics friends won't let me ask that question. It involves contradiction, or something.

But what I can do is point out that when you are stopped, your lights work normally. When you are going .5 c, your lights work normally. When you go .9 c, your lights work normally. When you go even faster, your lights work normally. There is no sense that, as you approach the speed of light, your lights are getting weirder and weirder. There is none of that at all.

And we know this because we do the experiment ourselves, every time we turn on a light.

Since Einstein we have known that motion is relative. The only sense in which one can move at any speed (or be stopped) is to move at that speed relative to something that is moving at that speed relative to you. So you are always stopped, and you are always moving near the speed of light.

If you cannot overlook the apparent impossibility of traveling near or at the speed of light, then let me ask this instead: if our planet within our solar system is orbiting the center of our galaxy at speed S, then is the speed of the particular light being shined from my super duper lantern essentially traveling at an increased speed of C minus S? I mean, if light can only go C and the first light wave automatically starts out traveling S, then it can't exceed the additional difference without it exceeding its maximum.

I have no clue what you're trying to ask, but the speed of light is the same for every observer.

 

[fast]

How fast are we moving relative to the speed of light?

 

[Wiploc]

How fast are we moving relative to the speed of light?

Since light is moving at the speed of light relative to us, the obvious answer is that we are moving at the speed of light relative to light.

But my physicist friends won't abide questions that involve moving at the speed of light, so maybe the obvious answer is somehow not the correct answer.

Further, deponent saith not.

 

[Bomb#20]

How fast are we moving relative to the speed of light?

The closest thing this relativistic universe offers to an absolute frame of reference is the cosmic microwave background radiation. We've measured its Doppler shift; it implies the earth is moving relative to the CMB at a little over 0.1% of the speed of light. So if you add up how fast the earth is going around the sun, how fast the sun is going around the center of the Milky Way, how fast the Milky Way is falling toward Andromeda, and how fast the Local Group is going relative to the CMB, that's what you should get. (And most of that is how fast the Local Group is going relative to the CMB.)

 

[Wiploc]

How fast are we moving relative to the speed of light?

The closest thing this relativistic universe offers to an absolute frame of reference is the cosmic microwave background radiation. We've measured its Doppler shift; it implies the earth is moving relative to the CMB at a little over 0.1% of the speed of light. So if you add up how fast the earth is going around the sun, how fast the sun is going around the center of the Milky Way, how fast the Milky Way is falling toward Andromeda, and how fast the Local Group is going relative to the CMB, that's what you should get. (And most of that is how fast the Local Group is going relative to the CMB.)

I don't see that as making sense. The CMB comes at us from all directions. We can hardly be, in any objective sense, going in all directions at .1% of the speed of light. And the speed of the earth and other local bodies has nothing to do with the CMB.

 

[Shadowy Man]

The closest thing this relativistic universe offers to an absolute frame of reference is the cosmic microwave background radiation. We've measured its Doppler shift; it implies the earth is moving relative to the CMB at a little over 0.1% of the speed of light. So if you add up how fast the earth is going around the sun, how fast the sun is going around the center of the Milky Way, how fast the Milky Way is falling toward Andromeda, and how fast the Local Group is going relative to the CMB, that's what you should get. (And most of that is how fast the Local Group is going relative to the CMB.)

I don't see that as making sense. The CMB comes at us from all directions. We can hardly be, in any objective sense, going in all directions at .1% of the speed of light. And the speed of the earth and other local bodies has nothing to do with the CMB.

The CMB does come at us from all directions, but there's a dipole asymmetry that suggests that we are moving relative to the CMB rest frame. See, e.g., http://astronomy.swin.edu.au/cosmos/C/Cosmic+Microwave+Background+Dipole

 

[Wiploc]

I don't see that as making sense. The CMB comes at us from all directions. We can hardly be, in any objective sense, going in all directions at .1% of the speed of light. And the speed of the earth and other local bodies has nothing to do with the CMB.

The CMB does come at us from all directions, but there's a dipole asymmetry that suggests that we are moving relative to the CMB rest frame. See, e.g., http://astronomy.swin.edu.au/cosmos/C/Cosmic+Microwave+Background+Dipole

Thanks.

 

[Angry Floof]

I like my steak brown on the outside and 50-75% pink in the inside. Is this rare or medium rare?

 

[beero1000]

I like my steak brown on the outside and 50-75% pink in the inside. Is this rare or medium rare?

 

[bilby]

I like my steak brown on the outside and 50-75% pink in the inside. Is this rare or medium rare?

View attachment 9261

The right-hand column should be titled "Obviously you don't like steak. Order the chicken."

 

[spikepipsqueak]

Can I befriend a feral cat without using food? Just wondering if there are any other ways.

It wouldn't be easy, if not impossible.

It would involve a lot of sitting very still over a really extended time frame, and a very curious target cat.

Ferals would usually favour discretion over curiosity.

 

[James Brown]

View attachment 9261

The right-hand column should be titled "Obviously you don't like steak. Order the chicken."

And the left-hand column should be titled, "Obviously you enjoy bacteria. Prepare your colon."

 

[bilby]

The right-hand column should be titled "Obviously you don't like steak. Order the chicken."

And the left-hand column should be titled, "Obviously you enjoy bacteria. Prepare your colon."

Bacteria are everywhere - and are abundant in a healthy human alimentary canal.

It is very hard to get sick from eating raw beef steak, unless you eat it a long time after slaughter, and/or store it in dreadful conditions. Only the surface is significantly colonised by potentially harmful bacteria; that's why steak can be safely served rare, but mince or ground beef (which is essentially nothing but surface) needs to be thoroughly cooked through.

Blue steak isn't in the slightest way dangerous to eat, unless you have a serious medical condition.

Well done steak is ruined no matter how healthy you are.

If food poisoning is your concern, then rare steak is far safer than cooked chicken, shellfish, or prawns. In fact, from a microbiological point of view, blue steak is one of the least risky things available. Oddly, the most serious food poisoning outbreaks in the modern developed world are caused by vegetables - it's safer to eat the beast that shits than to eat the plants it shits on.

There's no significant difference in the bacterial load between any of the steaks pictured on that chart.

 

[Angry Floof]

Dumb question of a legal nature: if you know something about someone and they offer, out of the blue, of their own accord, to pay you to keep their secret, is it still blackmail?

 

[George S]

Dumb question of a legal nature: if you know something about someone and they offer, out of the blue, of their own accord, to pay you to keep their secret, is it still blackmail?

If you take it, it could be used as evidence of blackmail about which you could be, in turn, blackmailed.

 

[Angry Floof]

Dumb question of a legal nature: if you know something about someone and they offer, out of the blue, of their own accord, to pay you to keep their secret, is it still blackmail?

If you take it, it could be used as evidence of blackmail about which you could be, in turn, blackmailed.

You're right, I didn't think of that. But it's icky all around whether technically illegal or not. Just curious. No one has yet offered me money to keep their secrets.

 

[beero1000]

Dumb question of a legal nature: if you know something about someone and they offer, out of the blue, of their own accord, to pay you to keep their secret, is it still blackmail?

I am not a lawyer, but I think that blackmail is illegitimately threatening to expose a secret for your own gain. The crime is making the threat, not getting paid - if you get caught before you received any payment you still committed the crime. If you didn't make the threat then it isn't blackmail. In reality though, if you're getting paid to keep a secret and someone accuses you of blackmail, you might have some problems demonstrating your innocence because of how it could look.