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/sci/ - Science & Math

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1893608 No.1893608 [Reply] [Original]

Hey /sci/!

Can someone tell me in detail why we cannot accelerate a particle without mass, a photon for example, above the speed of light?

I understand the principle of E=ymc^2 with y being the lorentz factor, but I dont grasp the idea of a massless particle being able to outspeed the speed of light.

When we're accelerating a photon for instance, does the energy start converting into mass? How does energy convert to mass, exactly?

Thanks in advance.

>> No.1893640

From the perspective of the photon, it is instantly arriving at its destination.

How can you reach something faster than instantly?

>> No.1893654

Well take a long distance then, one light year for example. It doesn't reach it's destination instantly.

>> No.1893671

>>1893654
in the reference frame of the photon, every distance is compressed to zero, thus taking exactly NO time to arrive. in the reference frame of an observer, the "inner clock" of the photon stands still thus the photon not measuring any time delay between start and arrival.

>> No.1893673

>>1893654
In fact it does. A photon is emitted, travels billions of light years, and is annihilated all at the exact same moment from its perspective,

>> No.1893674

>>1893654
From our frame of reference, no. From the photon's frame of reference, yes.

>> No.1893678

>>1893654
To it's perspective, no time passes at all.

That should tell you something.

>> No.1893681

>>1893640
Whoa I think you just indirectly made me understand tachyons.

>> No.1893690

But. If it's massless, does it really have a perspective from which we can look at things?

Genuinelyconfused.aiff

>> No.1893709

Massless particles can't be either accelerated or decelerated. It's like they have nothing to work with without mass - they can't change the angle of their world lines.

>> No.1893718

>>1893690
No.
A referential frame travelling at c or faster has no physical meaning. All we can do is make assumptions, from what we do know about frames travelling slower than c, but we can never be sure about it, due to the fact that we'll never be able toactually travel at c or faster.
According to relativity of course.