Cause and Effect

"Newton found that gravity is the cause of falling of an apple."
Is it true?
Saying gravity is the cause of falling of an apple is not true. Gravity alone cannot make any apple to fall. Presence of a gravitational field does not guarantee that an apple would fall.
If a cause cannot  individually and consistently produce an effect, then the cause is not a cause of the effect at all.
Can we say gravity is a cause among many other causes? No. If occurrence of many number of causes guarantees an effect, then the world is a completely predictable place. If we assume that the world is not predictable, then an effect cannot have a single cause or many causes.
For example,

1. There is an apple tree.
2. There is at least one ripe apple on it.
3. A wind is rocking the branches.
4. The tree is in a gravitational field.
5. There is a ground beneath.
6. There is enough light to see.
7. There is a man to report the fall.
8. The man is honest.
9. He knows English.
10. All the above are true.

Even with all these apparent causes if you are not confident enough that an apple would fall, then you have some idea about the working of the world. None of these individually or collectively guarantee anything. In other words, they do not cause anything, including the fall of an apple. So the word 'cause' does not mean what we mean by that word.

A Silent Happy Tree

Two eagles nested on a thorny tree with no green. I live on the seventh floor and have a top view on the whole tree. It had grown up to that height and suddenly branched into various directions. It is on that junction of four branches that the nest was built. It is not a lovely nest but it is an eagles' nest.
The tree showed no compassion. It was dry as if standing in the middle of a desert.
Yesterday I saw a baby. Light grey, in contrast to darker parents. There could be more babies.
But it is the tree which surprised me.
The thorny branches are now abundant with large red, very red flowers.
The tree must be happy now!

This could be some kind of Indian Coral tree.

There are snakes in the compound. Snakes like to drink eggs and eat newly hatched babies. But it is suicidal for any snake to raid an eagles' nest, that too upon a thorny tree. I don't know of crows, who are archenemies of eagles. Only a group attack can do any harm as a crow is smaller in size and weaker in confidence.

There are advanced ideas which would make General Theory of Relativity look like an SMS joke.