Speed of light

[kev100]

Albert Einstein told the world way back that no mass can travel at the speed of light which means that space travel is an impossibility, so why does the USA spend billions of dollars on something that we've known for a century can never be achieved?

Bearing in mind that the speed of light travels at a snails pace compared to the size of this galaxy so even at that speed we still couldn't go anywhere anyway.

[Dacetine]

By "USA" I presume you mean NASA? As I understand it NASA's mission is not to develop space travel but to improve our understanding of the cosmos. Sometimes this requires space travel (e.g. sending probes to other planets) but this should be regarded as the "means" rather than the "ends" and is not the goal of the whole venture.

[jake-the-peg]

Because you cannot paddle a canoe to New York doesn't mean you shouldn't go fishing across the bay!

The planetary science that we've been able to do with probes over the last half centuary has told us a gigantic amount about the Universe.

There is even the prospect of finding basic fossilised life on Mars.

Not to mention Hubble.

It's not about recreating Star Trek in real life

Or do you mean why do they spend so much on manned spaceflight?

The answer to that one is there is a lot of stuff that just can't yet be done by robots - repair of satellites etc. But most importantly it's major PR for NASA.

I think of it a bit like Formula 1 racing. Hugely expensive, debatable spin offs but necessary to keep interest levels (and funding) high for the important stuff.

[jake-the-peg]

PS You're wrong when you say that even at the speed of light we couldn't get anywhere.

Sirius is about 8 light years away if you were travelling at  0.999c then it would seem to anybody on earth that it would take you roughly 8 years.

But to you it would seem like 4 months.

But you are right in saying that it could never be achieved because your mass would also increase so the energy to get you to that speed would be unatainable

[kev100]

It would also take you another 8 years to get back, 16 year round trip, I know I wont be volunteering.

[stevie21]

Einstein got some things wrong you know. Not that I'm saying we can all travel at the speed of light (or faster) but it's unlikely that NASA are literally attempting such space travel.

[Flurfl]

NASA do spend money on "interesting" ideas for lightspeed and faster than light travel as part of their "breakthrough propulsion physics" program, but that program's budget isn't billions. NASA spend most of it's money on investigating the solar sytem, including earth, from space.

Relativity isn't the last word on the cosmos.

[janesmythe22]

A theory is never a fact, just an attempt to explain one or more facts.Einstein's theory of special relativity results from two postulates. By definition, a postulate is just an assumption (accepted without proof). So Euclid assumed his fifth "statement" to be a postulate...

[jake-the-peg]

Well Einstein's theory was a theory when it was put forward since then there have been an awful lot of experiments validating it.

My two favorites for time dilation are the flying of an atomic clock around the world and comparing it's time with another one on earth 

The second is that muons created in the upper atmosphere reach the earth when their half life is too short to let them survive the journey.

Both conveniently described here: http://www.physlink.com/Education/AskExperts/ae433.cfm

Physics is not like Maths. In Physics a theory is put forward and tends to retain the term theory even after vast amounts of evidence have supported it (eg Newton's theory of Gravitation) because unlike maths there can be no final proof, there is always the possibility of modification however remote. 

However, and here's something to ponder, the time diletion equations do not prohibit something travelling faster than light. They prohibit something travelling at the speed of light in theory. Past the speed of light you get a negative square root. Whether or not that has meaning nobody knows - we've never found a tachyon.

http://scienceworld.wolfram.com/physics/Tachyon.html

[druiaghtagh]

The speed of light cannot be exceede only by the KNOWN laws of physics at present, who knows what will be dicovered in the future. At the start of railway travel it was widely belived that the human body could not tolerate speeds of more than 30 mph, theories have a way of being improved upon or entirely disproved, i do not have the knowledge to say that faster than light travel is impossibel, it does not however stop me from believing it will become possible at some point in the future as scientific knowledge increases.

[Gef]

Good answer druiaghtagh. Also, there are two ways to achieve a shorter journey time - either go faster or find a shorter route.

[BillyBB]

And the human race needs to get off the planet before the sun expands into a red giant! We've got to start somewhere.

[Loosehead]

yep 4000,000,000 years, that's all we've got so make the most of it!

[Dacetine]

To respond to druiaghtagh's comment - technically Einstein's theory does not rule out travel at faster than the speed of light (hence physicist's speculation about "tachyons"), but only says that it is impossible to actually reach the speed of light - it is a boundary that cannot be crossed.