When Uranus was discovered they realised another planet must exist (Neptune) because of the “behaviour” of Uranus was being caused by Neptune.
What are they talking about? What was Uranus doing that showed Neptune was out there?
Thanks.
In: Planetary Science
Gravity.
Planets orbit around the Sun because of Gravity – the Sun pull them in, while inertia has them trying to “escape”. Without the Sun, they would each just fly in a straight line right out of the Solar System.
But gravity happens between all objects, not just planets and the Sun. Planets’ gravity also affect each other.
So, after astronomers discovered Uranus, they tracked its orbit around the Sun and realized that it doesn’t quite orbit the Sun predictably as you would expect. At that point Newton’s laws of gravity were already known for nearly 200 years, so you were able to predict an objects orbit around another object with a high level of accuracy. Uranus’s orbit however didn’t look right, it had some irregularities. These irregularities could only be explained if there was some other massive object nearby. They looked at where this object might be, and found Neptune.
Keep in mind it takes Uranus 84 Earth years to orbit the sun. As they were observing it they then used math to predict the path it would take. That path will then show how big it is and how far it is. Over time they kept finding inexplicable deviations from their predictions.
After enough data was gathered, someone then proposed that these deviations were caused by another planet’s gravity further out. People worked out the math, found where this other planet “should” be if it were to exist and when they pointed their telescopes there, lo and behold Neptune was discovered.
All objects with mass attract each other via gravity. The Sun has 99.9% of the mass in the Solar System, so *approximately* everything just orbits the Sun. But if you measure more precisely, you see that the planets also pull on each other. A planet that’s ahead of another one nearby is slowed down a bit, a planet that is behind another one is sped up a bit. If you measure the motion precisely enough then you can detect that effect, and if you see that effect without knowing a planet causing it then can conclude that some undiscovered planet must be somewhere nearby (“nearby” can still be over a billion kilometers here).
dude that’s wild. so basically Uranus wasn’t following the rules like it should have been. its orbit was all wobbly and stuff. so scientists were like hey somethin’s messin with Uranus and they figured it must be Neptune. it’s like finding out your friend is hiding snacks in their room cause they keep acting shifty in the kitchen.
so basically uranus was acting kinda weird like it was being tugged by something strong. astronomers were like wait what’s going on here. they figured there had to be another planet affecting it. turns out neptune was hiding out there just chilling and causing the weirdness. it’s like when your friend keeps shifting their weight trying to get comfortable but you don’t see the chair they’re on. super cool how they did all that math and figured it out without even seeing neptune at first. pretty impressive stuff honestly
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