Questions

There are approximately 6 trillion miles in a light-year, so the distance we need to go is 6 trillion miles / light-year times. 4 light-years is equal to 24 trillion miles. So, this whole would take 1.2 billion hours. There are 24 hours a day and 365.25 days per year, so this time in years is 137 thousand years.

The number of cell layers and cell types together give rise to 6 different types of epithelial tissue.

1. Simple squamous epithelia

2. Simple cuboidal epithelia

3. Simple columnar epithelia

4. Stratified squamous epithelia

5. Stratified cuboidal epithelia

6. Stratified columnar epithelia

Stratified squamous epithelia is best suited for areas subject to friction.

In 1985 the physicist Wilhelm Rontgen discovered X-rays, the "X" signifying their unknown origin.He later found that the rays could pass through flesh and by using photographic plates could make images of bones inside the body.