Tonight's Sky
Sun
Sun
Moon
Moon
Mercury
Mercury
Venus
Venus
Mars
Mars
Jupiter
Jupiter
Saturn
Saturn

Tonight's Sky — Change location

OR

Searching...

Tonight's Sky — Select location

Tonight's Sky — Enter coordinates

° '
° '

If photons have no mass, how can black holes gravitationally affect them? How can the huge gravity of a galaxy cluster bend their paths?

Richard Phelps, Plano, Texas
RELATED TOPICS: SPACE PHYSICS | GRAVITY
Objects like Earth warp space-time
Objects with mass warp space-time like you warp a trampoline’s surface when you step on it. When a photon is zipping through the universe, it has to follow the bends and curves of space-time — space-time is, after all, the only thing to travel through! So when the photon encounters a massive object, its path “dips” and “rises.” If you rolled a marble along the stepped-on trampoline, its path, too, would dip and rise.

Astronomy magazine subscribers can read the full answer for free. Just make sure you're registered with the website.

Already a subscriber? Register now!

Registration is FREE and takes only a few seconds to complete. If you are already registered on Astronomy.com, please log in below.
ADVERTISEMENT

FREE EMAIL NEWSLETTER

Receive news, sky-event information, observing tips, and more from Astronomy's weekly email newsletter.

ADVERTISEMENT
ADVERTISEMENT
BoxProductcovernov

Click here to receive a FREE e-Guide exclusively from Astronomy magazine.

Find us on Facebook

Loading...