Ten light seconds is a very long distance: 1.86 million miles (3 million Km). For comparison, the moon is about 1.3 light seconds from Earth and the shortest recorded distance between Earth and Mars is 187 light seconds.
Let us assume that an attacking battleship has the ability to lock onto a defending battleship ten light seconds away (this ability, whatever it is, does not benefit the defender). The energy beam is photonic and delivers approximately 109 joules of energy at a distance of ten light seconds. Let us also assume that the beam can be sufficiently focused that it arrives with no more than one meter of dispersion.
For the purpose of the question, let us assume the defending ship does not know the attacking ship is present.
Finally, let us assume that if the defending ship could detect the incoming beam with two seconds to spare, it could maneuver to avoid the attack. (Oh, and no shields. It's a whomping big problem for the defending ship to be hit by 109 joules of energy for any period of time.)
OK, one more thing. Ignore the length of time the energy weapon is activated. That's actually irrelevant to the question. Whether the beam was on an attosecond or all ten seconds of transit doesn't change the question.
Question: Is there anything about photons and/or space-time that we know or theorize today that would suggest it's possible for the defending ship to detect the incoming beam of energy before it strikes the ship (ideally two seconds before it hit the ship, but at all is the question)?
Please note the hard-science tag.
EDIT I apologize that I went to bed after writing the question and so didn't see any of the comments. It's obviously true that the photons, themselves, cannot be detected before impacting on the defending ship's sensors — which would suggest there's no way to detect the incoming beam. However, the Voyager space probe detected the bow of the solar magnetosphere and wind before passing into interstellar space, where it found hot plasma. It got me wondering if the passage of light might "push" something before it, like the bow of the solar magnetosphere or wind, and that incoming rush of "something" could be used to detect the incoming beam.
From this perspective it might be necessary to indicate where the attack is taking place, since the solar wind and magnetosphere are keeping most of the stuff that might be "pushed" out of the solar system, meaning it might be easier to have a successful detection in interstellar space. However, that might also simply mean it's harder inside a solar system, but not impossible. At worst, please consider both locations. If we all believe light can be used to push a space craft then it seems obvious that, so long as there is something to be pushed, that something could be used to detect the incoming beam.