Physics question about the speed of light

Innocent Bystander · Post by **Innocent Bystander** » Sat Jun 24, 2006 8:38 am

peeplj wrote:...I think you would reach critical mass before anything else happened....

Only if you were radioactive to begin with. Are you?

peeplj · Post by **peeplj** » Sat Jun 24, 2006 8:53 am

Innocent Bystander wrote:
peeplj wrote:...I think you would reach critical mass before anything else happened....
Only if you were radioactive to begin with. Are you?

Only when moving at speeds approaching c.

This usually only happens after eating hibachi.

--James

Azalin · Post by **Azalin** » Sat Jun 24, 2006 10:53 am

Darn nice thread James. It brings memories of a sci-fi book I read ages ago, about some people who wanted to go through some black hole in space, where time started to get distorted and all.

peeplj · Post by **peeplj** » Sat Jun 24, 2006 11:22 am

I liked the answers I got in the thread, but I wanted more of the "why."

So I read wikipedia's article on relativity, and it referenced an online article called "Albert Einstein's Theory of Relativity in Words of Four Letters or Less."

Here it is: http://www.muppetlabs.com/~breadbox/txt/al.html

This is an outstanding article...and it actually answered other questions I didn't even know I had. The bit about why the earth goes in a circle around the sun in particular is nice: it doesn't. It goes in a line. The sun's mass bends space and time around itself, so that the line looks like a circle when seen from one perspective.

It is a lasting regret that I never took physics.

Folks, thanks for some fascinating answers to my questions.

--James

BillChin · Post by **BillChin** » Sat Jun 24, 2006 12:12 pm

peeplj wrote:I liked the answers I got in the thread, but I wanted more of the "why."

So I read wikipedia's article on relativity, and it referenced an online article called "Albert Einstein's Theory of Relativity in Words of Four Letters or Less."

Here it is: http://www.muppetlabs.com/~breadbox/txt/al.html

This is an outstanding article...and it actually answered other questions I didn't even know I had. The bit about why the earth goes in a circle around the sun in particular is nice: it doesn't. It goes in a line. The sun's mass bends space and time around itself, so that the line looks like a circle when seen from one perspective.

It is a lasting regret that I never took physics.

Folks, thanks for some fascinating answers to my questions.

--James

Don't have too many regrets. College level physics requires a solid understanding of college level calculus. Even with that, I remember some of my physics classes. The median on tests often fell at 20% to 25% with 100% possible. This means the average student absorbed about 20% of the material. The lower level students probably less than 5%! And this was non-relativity physics, mechanics or electricity and magnetism.

I guess my point is that studying physics is considered hard, and even if a person studies it, only maybe the top 5% of students absorb much of it. If a person has trouble with thought experiments, through in a bunch of equations, plus complex mathematics and see how it mixes.

The holy grail of a grand unified theory is still out there. The current theories only explain a part of the observable universe.

Jack · Post by **Jack** » Sat Jun 24, 2006 12:15 pm

I have a friend who is a physics major and receives straight As in her courses. She's also an evangelical Christian. She has tried to explain to me how physics is a religious pursuit, but I admit that it's completely over my head.

peeplj · Post by **peeplj** » Sat Jun 24, 2006 2:05 pm

Cranberry wrote:I have a friend who is a physics major and receives straight As in her courses. She's also an evangelical Christian. She has tried to explain to me how physics is a religious pursuit, but I admit that it's completely over my head.

Myself, I keep trying to tie up String Theory and the Flying Spaghetti Monster...but as Cthulhu keeps eating the Spaghetti, it's turning into a bit of a knotty problem.

--James

pixyy · Post by **pixyy** » Mon Jun 26, 2006 2:52 am

Most of this stuff boggles my mind, but it is really fascinating!
This site http://www.spacetimetravel.org/ has a lot of visualisations of speed of light travels. Some really neat stuff.

(about half of it is in Deutsch though, which is about as incomprehensible as time travel itself....)

Borderpiper · Post by **Borderpiper** » Mon Jun 26, 2006 5:35 am

I've got a quick (probably stupid) question....

If you were blind you sound would be your main reference to somethings location; disregarding touch for the time being. This would work fine for things that travel at low speeds but as soon as you had to pinpoint the location of say a jet plane you would always point too far behind it; assuming it was traveling at more than 330ms. You would think that the speed of sound was a natural speed limit because you couldn't hear an object traveling faster then this. You would need someone sighted to tell you that something was actually traveling faster.

Now say you were sighted and something was traveling faster than the speed of light how would you know? Like the blind person you have no other way of telling where the object is? You would think that the speed of light was a natural limit.

David

djm · Post by **djm** » Mon Jun 26, 2006 9:10 am

No-one has measured the speed of thought ....

djm

chas · Post by **chas** » Mon Jun 26, 2006 9:49 am

Borderpiper wrote:I've got a quick (probably stupid) question....

If you were blind you sound would be your main reference to somethings location; disregarding touch for the time being. This would work fine for things that travel at low speeds but as soon as you had to pinpoint the location of say a jet plane you would always point too far behind it; assuming it was traveling at more than 330ms. You would think that the speed of sound was a natural speed limit because you couldn't hear an object traveling faster then this. You would need someone sighted to tell you that something was actually traveling faster.

Now say you were sighted and something was traveling faster than the speed of light how would you know? Like the blind person you have no other way of telling where the object is? You would think that the speed of light was a natural limit.

Not a stupid question at all; I hope I don't give you a stupid answer.

We would have to make indirect observations in order to see something like what you describe. The most useful would probably be some sort of mass or gravitational measurement. This is how we observe black holes. Many calculations suggest that 90% of the mass of the universe is unaccounted-for. This is so-called "dark matter," which means we can't see it. It's quite possible that some of this is faster-than-light matter (hot dark matter). These faster-than-light particles have been dubbed tachyons.

Chiffed · Post by **Chiffed** » Mon Jun 26, 2006 11:31 am

peeplj wrote:
Innocent Bystander wrote:
peeplj wrote:...I think you would reach critical mass before anything else happened....
Only if you were radioactive to begin with. Are you?
Only when moving at speeds approaching c.

This usually only happens after eating hibachi.

--James

Radioactivity can approach zero, but does not equal zero. As mass went critical, you'd experience the slowest, darkest nuke reaction ever (from inside it, experiencing time dilation).

From the outside, you'd be a big, bright, fast smear. Just don't stick yer feathers on with wax.

BillChin · Post by **BillChin** » Mon Jun 26, 2006 10:39 pm

If time slows down as an object approaches the speed of light, one amateur conclusion to grasp at, is that time goes negative if an object exceeds the speed of light. The other sci-fi-type conclusion is that the object can exist in all places at a single moment, by varying how much its speed exceeds C.

I think I know why I got about the median on those physics exams (about 25% out of 100% for those paying attention)...