They have to have *some* measurable mass, for solar sails to work... granted, there's more than sunlight hitting a solar sail, but still...

The theory is that photons have momentum, but still no mass. 

http://en.wikipedia.org/wiki/Radiation_pressure

Quantum theory argument

From the perspective of quantum theory, light is made of photons: particles with zero mass but which carry energy and —importantly in this argument— momentum . According to special relativity, because photons are massless their energy (E) and momentum (p) are related by E=pc.[7]

Now consider a beam of light perpendicularly incident on a surface, and let us assume the beam of light is totally absorbed. If we imagine the beam is made of photons, then every second numerous photons strike the surface and are absorbed. The momentum the photons carry is a conserved quantity—that is, it cannot be destroyed—so it must be transferred to the surface; the result is that absorbing the light beam causes the surface to gain momentum.

Newton's Second Law tells us that force equals rate of change of momentum, so during each second the surface experiences a force (or pressure, as pressure is force per unit area) due to the momentum the photons transfer to it. We have:

Pressure = momentum transferred per second per unit area = Energy deposited per second per unit area / c = I/c.

Where I is the intensity of the beam of light (measured in e.g. W⋅m−2).

In the above argument we assumed that the surface totally absorbed the beam, in general light can be transmitted, reflected and/or absorbed. If the light were totally reflected then the radiation pressure is doubled compared to total absorption, this is because the photons arrive with momentum E/c and depart with momentum -E/c (the -ve sign indicates traveling in the opposite direction), so the change of momentum is 2E/c.

(Serious question)

A proton is an object too, right?  Why is sun light not infinitely heavy then?

 

I am guessing you mean "photon" not "proton".  The protons ejected by Sun are not moving at c ("c" is geek speak for "speed of light in a vacuum").

One of the consequences of Special Relativity is that matter and energy are just different aspects of the same thing, Cleverly, this is called "matter-energy".  They are related by the famous equation, E equals Em Cee squared.

A photon has a zero REST mass.  "Rest" in this case mean not moving relative to your frame of reference.  That means that if you could stop a photon and cool it to absolute zero, it would have zero mass.  But a photon in our frame of reference has energy and energy is mass. If it has mass and velocity, then it has momentum.  I know that above is hard to understand and I ma not the best teacher in the world.  It took me quite a bit of skull sweat to grok Relativity and I'm still not sure I do.

As I remember the story, the invention does not create an antigravity field so much as negate the influence of all gravity on an object in the field.

Which is why the field glows: atoms are accelerated out of the field, but resume normal velocity when they leave it.

The billiard ball doesn't "take off at the speed of light", so much as "come to a dead stop in relation to the planet, the solar system, and the Milky Way". And since everything else keeps moving... it punches a hole through the braggart that invented it, etc.  The assumption is that it will eventually start moving again.

.......OTGH, .......

I see what you did there. 

you mean the house exploded with the force of a giga-ton nuke? an object moving anywhere measurably near the speed of light carries a ridiculous amount of energy. (think about a single grain of sand having the muzzle energy of the Paris gun.) which is why any one reading the latest draft of Cobalt will notice that speeds are now given in KPS instead of increments of Cee. (the handguns were shooting tzar bombs...)

I'm thinking it punched holes in the objects ... as best as I recall.

As I remember the story, the invention does not create an antigravity field so much as negate the influence of all gravity on an object in the field.

Which is why the field glows: atoms are accelerated out of the field, but resume normal velocity when they leave it.

The billiard ball doesn't "take off at the speed of light", so much as "come to a dead stop in relation to the planet, the solar system, and the Milky Way". And since everything else keeps moving... it punches a hole through the braggart that invented it, etc.  The assumption is that it will eventually start moving again.

I don't remember it being that way .... I'm going to have to see if one of my Asimov collections has that story and reread it.  It's been forty years atleast .... so my memory may not be as accurate as yours.   

http://en.wikipedia.org/wiki/The_Billiard_Ball There we go...

An example of Asimov's "late style",[1] the story is a journalist's recollection of the events surrounding the discovery of an anti-gravity device in the mid-21st century. Heavy with physics theory, the story describes the relationship between the creator of the device, the billionaire inventor Edward Bloom, and his former classmate James Priss, a Nobel Prize-winning theoretical physicist who had discovered most of the theory that made the device possible. The men are expert billiards players and bitter rivals. Challenged to execute a shot on a table which is equipped with the device, Priss sends a ball on a complicated trajectory which finishes when it enters the device's field. At that point the ball vanishes and Bloom collapses, dead. There is a mysterious hole drilled completely through his chest.
 
Central to the story is the concept of a pure anti-gravity machine that turns out to be a perpetual motion machine of the 1st order. Energy can be freely created in a volume of space time which is pulled 'flat' as defined within the Theory of Relativity as determined by Einstein. However, this field possesses remarkable properties, which are the centerpiece of the story: any object which enters the field is reduced to zero mass, and hence must assume the speed of light. There is also the unprovable speculation as to whether Priss knew, from his own theory and the nature of the blue glow produced by the field (possibly due to Cherenkov radiation), what would happen, and if he then directed the ball in such a way as to kill Bloom.

IIRC, the stargate from the movie and television franchise disassembled the object at the origin, sent it as a stream of subatomic particles (presumably there was some reassembly instructions included  ) and reassembled it the terminus. The wormhole was a conduit to move the disassembled object FTL.  I read in some article or another the reasoning was that the theoretical description of wormholes only allows for subatomic particles to be "tunneled".

Really just a variation of the FAX type teleporter but without the messy problem of duplicates.

The Stargate is what you would call more of a mirror point. An artificially created 'fold' in spacetime. So there is no need for subatomic particulation. But the portal energy would have to be immense.
As sparkly as hollywood makes it doesn't mean its real. Fanciful and flashy. But unrealistic.


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Only that it would also affect spacetime as well.
Nuetronium spinning at the apeed of light would be awesome to see.

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And all the time I thought all you needed was a DeLorean.

Try it in a Yugo....I dare ya!

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Not enough room for the flux capacitor.

You could probably fit it in the passenger seat.

http://www.oreillyauto.com/site/c/detail/EB00/121G.oap