What does a blank tile mean in words with friends?

dear friend:

  i hope this letter finds you in soaring spirits and vibrant health. as you had expressed the wish to know about culture, traditions, and unity of india in your previous letter, in the following lines i have tried my best to give you glimpses of our culture, traditions, and unity. you will be amazed to know that our culture is the oldest culture in the world and the birth place of hinduism, buddhism, jainism, and sikhism. you won’t find any other culture as varied and multi-colored, multi-lingual as ours. each region has its own unique culture, traditions, language. there are 22 official languages in india.

  basically, india is a spiritual country with orthodox traditions. for example the people of india believe in traditions set by their wise forefathers. arranged marriages, joint-family system, universal brotherhood, vegetarianism, celebrating festivals such as diwali, holi, eid, etc., are the salient features of our culture and traditions.

  another unique aspect about our country is ‘unity in diversity’. in spite of the multi-lingual, multi-religious, multi-traditional, multi-cultural society, people live peacefully together, respecting one another’s views, cultures, traditions, and differences. i am sure you would love to visit india soon, and have a first-hand experience of the multi-colored culture. give regards to uncle and aunt. do visit india with your family and experience our hospitality.

your friend,

giant impact theory - the moon was formed from the collision between earth and another mars-sized body.

colliding planetesimals hypothesis - the moon was formed from the same cloud of material as earth.

capture hypothesis - the moon was locked into orbit by earths gravity as it was passing by it.

accretion hypothesis - the moon was formed from collisions and combining of planetesimals.

i think this is right, if not and you know better let me know.