Currently physicists require that massless particles such as photons move at the velocity of light relative to particles with mass. So for a modified version of Einstein’s thought experiment in which:

1) you recede from the photon’s source,

2) are caught up with by the photon, and,

3) absorb it,

the photon’s measured velocity must be independent of your velocity.

Moreover, Einstein’s rejection of a light-carrying “ether” forestalls any direct observation of light’s transverse vibrations in that medium. Such waves are now invoked only mathematically: to calculate an emitted photon’s likely point of arrival. So the photon must actually be absorbed somewhere for it’s velocity or wavelength to be measured — one can never observe the wave itself. One might say that light as a vibration in a medium was abandoned but not the mathematical wave associated with that vibration. (The Cheshire cat gone, but not its smile; the physical vibration gone, but not it’s Platonic Form, the sine wave.)

But there is an interesting wrinkle: your recessional velocity does affect the measurement of the photon’s wavelength. So for the above version of Einstein’s thought experiment the faster you recede, the longer the absorbed photon’s wavelength (this is the famed Doppler Effect). More specifically, the absorbed photon’s wavelength would trend toward infinite the faster you receded from the photon’s source, or the faster the source receded from you, which under relativity is the same thing.

Of course, Einstein’s version of the above thought experiment required moving at the speed of light and so proved impossible in principle. Perhaps for that reason it was of limited help to him. Special Relativity appears to have been inspired more by his dissatisfaction with Maxwell’s equations and by a sudden insight into the non-absolute nature of time.

Less clear is the role played by patent applications for synchronized railway clocks, a hot topic at that time, and one that may have helped nurture this sudden insight. The following book explores the role that early 1900s clock synchronization technology may have had on Einstein’s and Poincare’s development of relativity:

http://www.amazon.com/gp/aw/d.html/ref=redir_mdp_mobile/175-1776894-6543643?a=0393020010

Which reminds me: Rawls probably belongs among my “great thinkers”, wouldn’t you say?

I’m a huge fan of thought experiments… especially as they apply in wider contexts. I recently read Alison Gopnik’s (philosopher and developmental psychologist – and sister of Adam) latest book “Philosophical Baby”.
http://search.barnesandnoble.com/The-Philosophical-Baby/Alison-Gopnik/e/9780374231965
Her main thesis is that the ability to perform thought-experiments (imagining alternative futures, ‘what if planning’ – she calls these all ‘counterfactual’ thinking) is one of the key things that distinguishes us as humans.

And my favourite such counter-factual thought experiment is from Rawls in constructing his theory of justice – he thinks the best way to design the rules of a society is by imagining (i.e. thought-experimenting) how those rules work as seen from behind a “veil of ignorance” as to what position you (or each individual) have/has (or will have). Not knowing if you are blessed with strengths encourages you to opt for the set of rules that would be fairest to all. Didn’t explain that well – but as ever there is a good wiki easily a click near by
http://en.wikipedia.org/wiki/A_Theory_of_Justice
Warren Buffet calls this the ‘ovarian lottery’

If only we applied such thought-experiments more widely (e.g. in health care debate).

Me and my economist friend was talking about the Chinese judicial system and I got us into talking about how would China gets herself into a fair and equitable judicial system. Kind of a “thought experiment” where what if we were ruling China, how would we get out of this mess.

At the moment, many court cases (those prominent and important enough to be reported by the media) were still show trials. For example, deciding a case in a few short days and sentencing someone to death is a bit too efficient. There was a Canadian model that got murdered in China and the Chinese police were very efficiently (may be too efficiently) in finding “the killer” and sent through the courts. Case close. And then there were many cases of those lawyers that fight for workers’ and human rights in China, and these lawyers being harassed and even arrested by the police/government for doing their legal work.

Anyway, my friend was more willing to accept the possibility of gradual changes leading to a fair and equitable judicial system. Where I think the Chinese judicial system is not something that gradual changes work.

To me, if and when the Chinese leaders want to change the judicial system and make it a “fair and equitable” one, it has to be a wholesale change from the lowest to the highest court. A judicial system tends to break at its weakest link.

If you’re on a tight budget, keep meditating.

Is there a legal way to attempt reaching the speed of light? I’d like to give this a go. Becoming a massless journalist and all that.