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We know that photons (light) are massless but they have momentum. Now suppose I am in the space far away from planets/stars that there is no external force exerts on me, if:

1- I turn on a flashlight (torch), would I be pushed in the opposite direction which the flashlight is facing (Newton's third law)?

2- If a star is shedding light on me (its photons hit my body), would I start moving due the impact of the photos?

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    $\begingroup$ See How can a red light photon be different from a blue light photon? $\endgroup$
    – mmesser314
    Commented Aug 12, 2020 at 13:12
  • $\begingroup$ I've removed a number of comments that were attempting to answer the question and/or responses to them. Please keep in mind that comments should be used for suggesting improvements and requesting clarification on the question, not for answering. $\endgroup$
    – David Z
    Commented Aug 13, 2020 at 0:10

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Yes in both cases. In fact there is no need to invoke the concept of photons; electromagnetic radiation consistent with Maxwell's equations carries momentum.

You might care to search online for articles on photon propulsion and solar sails.

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    $\begingroup$ Note that it takes a lot of energy. For light, $E=pc$, so (for example) to give 1 kg an impulse of 1 m/s takes almost 300 megajoules. $\endgroup$
    – PM 2Ring
    Commented Aug 12, 2020 at 11:51
  • $\begingroup$ which is why there are many proposals for practical applications but few if any actual implementations. $\endgroup$
    – Philip Wood
    Commented Aug 12, 2020 at 12:00
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    $\begingroup$ @PM2Ring "lot of energy" -- everything is relative to what you expect :-) . A supernova will produce enough photons to accelerate the crap out of your General Products Number 4 Hull. $\endgroup$
    – Carl Witthoft
    Commented Aug 12, 2020 at 12:47
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    $\begingroup$ @Carl Sure, but if you're that close to a supernova, even the neutrino (& antineutrino) flux will make things "interesting". On the topic of supernova energies, please see physics.stackexchange.com/a/455549/123208 ;) $\endgroup$
    – PM 2Ring
    Commented Aug 12, 2020 at 12:51

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