Below is the list of tables from the database along with their columns and datatype. Need to generate an accurate SQL query for the question.
Only use the columns present in the respective table. Only use the columns which are required to generate the SQL query. Only use table joins if required and not otherwise.

### Tables ###
TABLE: CREATE TABLE table_55501 ( "Ship's name" text, "Entered service" text, "Ended service" text, "Gross Tonnage" real, "Type of Vessel" text )

### Question ###
I want the total number of gross tonnage when entered service was 1903

### Accurate SQL ###

SELECT COUNT("Gross Tonnage") FROM table_55501 WHERE "Entered service" = '1903'